1. Field of the Invention
The present invention relates to hydrocyclone separators used for separating components of fluid mixtures and, more particularly, to such hydrocyclone separators that are used to separate small quantities of oil from large volumes of water.
2. Setting of the Invention
The use of hydrocyclone separators for the separation of components of fluid mixtures is well known, such as disclosed in U.S. Pat. Nos. 3,306,461, 4,544,486 and 4,698,152. In such hydrocyclone separators, a liquid stream is fed tangentially into an upper cylindrical portion where the liquid is accelerated in a spiral as the liquid flows through a conical lower portion. As the liquid spirals, centrifugal forces draw the more dense components to the outer portion of the rotating column of liquid and the less dense components of the liquid migrate to a central column area. The dense components are discharged through a lower underflow opening in the conical lower portion and the less dense components are passed upwardly through a centrally located overflow opening or outlet.
It has been found that a plurality of hydrocyclone separators used in series can be more efficient in separating the components than using a single stage hydrocyclone. Various hydrocyclone separator systems have been used in the past that included several hydrocyclone separators used in series. Therein, the less dense components of a first hydrocyclone separator are introduced into a second hydrocyclone separator. The less dense components exit the first hydrocyclone separators as a rotating, upwardly traveling fluid stream wherein the higher density components are already at the outer periphery before the stream is introduced into the second hydrocyclone separator. However, the rotating stream's rotation is stopped or greatly diminished by the conduit or piping used, thereby causing the semi-separated higher density components to be remixed prior to being introduced into the second hydrocyclone separator. U.S. Pat. No. 4,711,720 discloses a hydrocyclone separator system wherein the overflow from a first hydrocyclone separator is tangentially passed into at least one secondary hydrocyclone separator in a manner preventing the higher density semi-separated components from being remixed. In this specific application, this arrangement is not beneficial. Specifically, hydrocyclone separators are being utilized for the separation of small quantities of oil from large volumes of produced water. It is necessary to retain the spinning momentum of the fluid as the fluid traverses from the underflow of the first cone to the feed of the second cone.
Thus, there is a need for improved hydrocyclone separation systems which can take advantage of the general principles described in U.S. Pat. No. 4,711,720 to improve the separation efficiency of hydrocyclone separator systems used in removing oil from water.